Built in sub crossover

Are you contemplating a high pass connection to accommodate a pair of small speakers?

As far as I can tell the NHT B12d and SW12 are not equipped with low level (RCA) outputs or a high pass function. Both have fixed crossover selectors and low pass knobs.
Judging from a poor photo of the SW12 rear panel it seems to have a high level (Speaker) spring clip input only connections.

I can't find a manual or rear photo for the more expensive CS12.

While NHT produces economical products their functionality is usually better than acceptable.

I've ran my pre amplified front ends through a number of Velodyne and one JL Audio F Series subwoofer with little to no affect on the presentation yet I choose to run the main speakers full range.    

   

Some dyn floor standers and svs 12" subs

I run my system through my JL audio’s Built in E112 crossovers and I can’t hear a difference. The subs are the cheapest part of my system. 

Like all things it will come down down to implementation. 

Ben, Please pardon me, I have no idea why I thought you're using NHT subs. 

I used to.